Kansas on Tuesday became the 18th and latest state to pass a constitutional amendment barring gay marriage. With conservatives pushing to define marriage as between a man and woman throughout the country, similar proposals are on the ballot in three other states next year and more than a dozen are considering them.

New England has been the major holdout; there, legislators and judges have strengthened rights for gays and lesbians. The Connecticut Senate on Wednesday voted to legalize civil unions. If the bill becomes law, Connecticut would be the only state to do so without a court order demanding lawmakers act.

Kansas voted by a more than 2-to-1 margin Tuesday to ban gay marriages and civil unions, and voters also ousted the lone gay city council member in Topeka, Tiffany Muller, who had defeated an emphatically anti-gay opponent in the primary.

New England seized on by both sidesThe New England examples — most decisively Vermont’s civil unions and Massachusetts’ legalized gay marriages — are seen by ban supporters as the threat that’s helping their cause. Advocates for gay marriage also see those examples as a plus, by proving that fears gay marriage will somehow destroy society’s social fabric are unfounded.

“The more places that we are able to extend the same rights and responsibilities to all Americans, the more places we’ve got a light to shine on what’s happening,” said Joe Solmonese, president of Human Rights Campaign, a gay rights lobbying group.

“Massachusetts, the last time I checked ... is still there. Marriage is still there,” he said. “People are going on with their lives, gay and lesbian couples are raising their families and living their lives like everyone else. None of what has been forecasted or what we’ve been warned about seems to have happened there.”

New England states aren’t the only ones to offer gay rights activists hope. California, Hawaii and New Jersey also allow for domestic partnerships — though California and Hawaii also have state laws that define marriage as between a man and a woman.

Connecticut offers the strongest recent pro-gay legislation, by extending all rights and privileges of marriage to same-sex couples but without an actual marriage license.

Connecticut House likely to go alongOn Wednesday, the state Senate voted 27-9 to recognize civil unions; proponents say the bill will likely clear the House — also controlled by the Democrats — possibly as early as next week. Republican Gov. M. Jodi Rell has not taken a stand on the bill, but has said she supports the concept of civil unions.

In Maine, a new law signed last month protects gays and lesbians from discrimination, though it made clear it doesn’t extend the rights of marriage. The state already allows for domestic partners, who could be homosexual or heterosexual, many of the legal rights of marriage, such as rights to inheritance and benefits.

New Hampshire set up a commission to study civil unions after legislators last year refused to recognize gay marriage.

For ban supporters, the key difference is a vote of the people.

“When the people are given a chance to decide, their view is overwhelming,” said Peter Sprigg at the conservative Family Research Council. “Every state that had this on the ballot passed it. It shows to me there is a tremendous grass roots consensus that marriage is between a man and a woman.”

Votes coming in Alabama, South Dakota, TennesseeVoters will decide the question in Alabama in June 2006, and in South Dakota and Tennessee at the 2006 election. Bills are also moving forward in Minnesota, South Carolina and Texas to put the measure on the ballot there.

Meanwhile, courts are continuing to hash out the dispute, giving hope to both sides. A California state judge ruled last month that the state law banning gay marriage was unconstitutional and that gay couples can marry. A New York state judge ruled along similar lines in February. Both decisions are under appeal.

“To be frank, every time one of those decisions comes down it just adds fuel to the fire for our efforts,” Sprigg said. “Courts are trying to take the decision out of the hands of the people.”

Yale law Professor William Eskridge, a constitutional scholar active in support of gay rights issues, said that, in the end, New England won’t be the lone holdout, and expects resistance to the bans across the Northeast and the West Coast.

But much of the rest of the country would likely back a ban, he said, predicting as many as 40 states would adopt them. Ultimately, the dispute will be decided by the U.S. Supreme Court.

And by then, years of gays and lesbians living as partners recognized by Massachusetts, Vermont and elsewhere will test the warnings of critics that gay marriage is a threat to the institution of marriage, he said.

“Now we have laboratories to observe whether these predictions would come true,” Eskridge said. “Now we can wait to see who’s right.”